The world's oldest person turned 116 yesterday - as health chiefs in Japan launched a study to find out why he and many of those around him have lived so long. Jiroemon Kimura, who was born in 1897, was expected to celebrate his astonishing milestone with friends and family. He was also to be visited by the mayor of his home city, Kyotango, in the west of the country. Kimura is one of 95 people aged 100 or more in the city's 60,000-strong population. He does not smoke, drinks only a "modest" amount of alcohol and has made it a practice to eat only until he is 80 per cent full, a local official said. His motto in life is "to eat light and live long", the official added. Kyotango now wants to find the secret of his longevity and has launched a research project. "We would like to research the eating habits of not only Mr Kimura but also about 50 other old people over 100 years old in the city," the official said. "We are interested in what they eat and how much. We are especially keen to look at how much salt they consume." The city, near Kyoto, is sandwiched between the Sea of Japan (or East Sea) and a mountain range. It is naturally blessed with good seafood and farm products. "We are also interested in knowing what kinds of local food they like to eat and finding out whether this helps them to live so long," the official said. "We want residents to know of the secrets of what enables a long life-span but also to attract tourists to this long-living city."